Quantum Droplet, or Dropleton - What is it?

It usually takes years for physicists to find new particles that illustrate the many aspects of the laws of nature. Perhaps not being able to stand the wait, an international team decided to come up with their own particles.

These particles were named “dropleton” or “quantum droplet” and are actually clusters of short-lived electrons and “holes” which are positive charges. Just like other so-called “quasiparticles,” these dropletons also have a tendency to act like single particles.

What is a Quantum Droplet?

In Germany, at the Philipps-University of Marburg, and at the Joint Institute for Lab Astrophysics located at the University of Colorado, researchers came up with an agglomerate of holes and electrons that turned out to be so much bigger than anything they have come up with in previous years. The agglomeration they came up with measured 200 nanometers (billionths of a meter). While that may not seem like a big deal to some since it is still too small to see with the naked eye, what bears remembering is that this is a particle they are talking about and in the particle world, this is a virtual behemoth. If compared to something, this agglomeration is about one-50th the thickness of a single cotton fiber and may be seen using a good telescope.

Before this discovery, physicists were able to create two-pair groups of holes and electrons but never were they able to come up with an agglomeration such as this which is capable of forming the unique liquid-y “dropleton” or “droplet”, as it is also called.

These dropletons or droplets behave in a way that adheres to the rules of Quantum Physics. What this means is scientists and researchers are able to utilize the particles in experiments that involve light interacting with matter.

In a February issue of the journal Nature, scientists state that due to the massive size of the droplets, they hope that this will help them determine the boundaries that lie between the classical world of the human scale and the quantum world.

How Quantum Droplets were Made

According to Phillips University physics professor Mackillo Kira and his colleagues at the Joint Institute of Laboratory Astrophysics, to make the droplets, they fired pulses of light from a powerful laser directly at a block of gallium arsenide. This is the same material they found in LEDs or light-emitting diodes. The pulses of light were not held for very long and they lasted just 100 femtoseconds which is about billionths of a billion of a single second. As soon as a pulse of light made contact with the gallium arsenide, atoms became excited which means they released electrons which then moved around within the material in the form of plasma or gas. As soon as the electrons, negatively charged, left the areas around atoms, what was left behind were areas of holes or areas of positive charge.

In an email sent to Live Science, Professor Kira stated that the dropletons were, in a sense, particles with properties that are determined largely by the environment and this is what makes them so exciting. Kira also said that semiconductors were best for these particles because their electrons are arranged in such a way that are easier to excite.

Given that it is an artificial particle, the droplet contains a lot of elections and therefore acts like a massive electron. This means that physicists can have more freedom in their experiments since they can change the size of the electrons to get different results. Professor Kira then noted in the same email to Live Science that this will allow researchers, scientists, and physicists, to engineer a man-made mass for an electron. Something that is entirely different from using the universal constant that is measured in free space.

When electrons and holes have opposing charges and when they come together, they form “excitons” (term for paired holes and electron). Of all the electron-hole particles that scientists have come up with, dropletons are the only ones to have enough pairs to actually form a droplet that is liquid-like. People who have used some types of solar panels will be familiar with these electron-hole pairings since panels use special materials to divide electron-hole pairs which then frees electrons that results in currents.

The excitons found in droplets are more energetic though and they contain such a high amount of energy that they tend to move together in clumps which is similar to what actual water droplets to. When they come together in this formation, they cease to be excitons and are known as dropletons. The thing about these dropletons is they do not have very strong lasting power and last just a trillionth of a second (23 picoseconds). However, when viewed in the context of the quantum-physical process, it is actually quite long. Scientists hope that by studying these dropletons, they can better understand and design optoelectronic devices that make use of fiber optics.

Have you heard of Quantum Droplet or "Dropleton" before reading this article?